The Hpa-tg mice had an overall lower proportion in thymus of CD4+CD25+Foxp3+ (Fig. 6a), CD4+CD25+Foxp3+Helios+ (Fig. 6b) and CD4+CD25+Foxp3+Helios− (Fig. 6c) T cells, which is well in line with the more severe pathology of RA in the Hpa-tg mice. Here, CD4 is linked to rheumatoid arthritis.